/**************************************************************************** * * * GNAT COMPILER COMPONENTS * * * * T R A C E B A C K * * * * C Implementation File * * * * Copyright (C) 2000-2004 Ada Core Technologies, Inc. * * * * GNAT is free software; you can redistribute it and/or modify it under * * terms of the GNU General Public License as published by the Free Soft- * * ware Foundation; either version 2, or (at your option) any later ver- * * sion. GNAT is distributed in the hope that it will be useful, but WITH- * * OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY * * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * * for more details. You should have received a copy of the GNU General * * Public License distributed with GNAT; see file COPYING. If not, write * * to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, * * MA 02111-1307, USA. * * * * As a special exception, if you link this file with other files to * * produce an executable, this file does not by itself cause the resulting * * executable to be covered by the GNU General Public License. This except- * * ion does not however invalidate any other reasons why the executable * * file might be covered by the GNU Public License. * * * * GNAT was originally developed by the GNAT team at New York University. * * Extensive contributions were provided by Ada Core Technologies Inc. * * * ****************************************************************************/ /* This file contains low level support for stack unwinding using GCC intrinsic functions. It has been tested on the following configurations: PowerPC/AiX PowerPC/VxWorks Sparc/Solaris i386/GNU/Linux i386/Solaris i386/NT i386/OS2 i386/LynxOS Alpha/VxWorks Alpha/VMS */ #ifdef __alpha_vxworks #include "vxWorks.h" #endif #ifdef IN_RTS #define POSIX #include "tconfig.h" #include "tsystem.h" #else #include "config.h" #include "system.h" #endif extern int __gnat_backtrace (void **, int, void *, void *, int); /* The point is to provide an implementation of the __gnat_backtrace function above, called by the default implementation of the System.Traceback package. We first have a series of target specific implementations, each included from a separate C file for readability purposes. Then come two flavors of a generic implementation: one relying on static assumptions about the frame layout, and the other one using the GCC EH infrastructure. The former uses a whole set of macros and structures which may be tailored on a per target basis, and is activated as soon as USE_GENERIC_UNWINDER is defined. The latter uses a small subset of the macro definitions and is activated when USE_GCC_UNWINDER is defined. It is only available post GCC 3.3. Finally, there is a default dummy implementation, necessary to make the linker happy on platforms where the feature is not supported, but where the function is still referenced by the default System.Traceback. */ #define Lock_Task system__soft_links__lock_task extern void (*Lock_Task) (void); #define Unlock_Task system__soft_links__unlock_task extern void (*Unlock_Task) (void); /*-------------------------------------* *-- Target specific implementations --* *-------------------------------------*/ #if defined (__alpha_vxworks) #include "tb-alvxw.c" #elif defined (__ALPHA) && defined (__VMS__) #include "tb-alvms.c" #else /* No target specific implementation. */ /*----------------------------------------------------------------* *-- Target specific definitions for the generic implementation --* *----------------------------------------------------------------*/ /* The stack layout is specified by the target ABI. The "generic" scheme is based on the following assumption: The stack layout from some frame pointer is such that the information required to compute the backtrace is available at static offsets. For a given frame, the information we are interested in is the saved return address (somewhere after the call instruction in the caller) and a pointer to the caller's frame. The former is the base of the call chain information we store in the tracebacks array. The latter allows us to loop over the successive frames in the chain. To initiate the process, we retrieve an initial frame pointer using the appropriate GCC builtin (__builtin_frame_address). This scheme is unfortunately not applicable on every target because the stack layout is not necessarily regular (static) enough. On targets where this scheme applies, the implementation relies on the following items: o struct layout, describing the expected stack data layout relevant to the information we are interested in, o FRAME_OFFSET, the offset, from a given frame pointer, at which this layout will be found, o FRAME_LEVEL, controls how many frames up we get at to start with, from the initial frame pointer we compute by way of the GCC builtin, 0 is most often the appropriate value. 1 may be necessary on targets where return addresses are saved by a function in it's caller's frame (e.g. PPC). o PC_ADJUST, to account for the difference between a call point (address of a call instruction), which is what we want in the output array, and the associated return address, which is what we retrieve from the stack. o STOP_FRAME, to decide wether we reached the top of the call chain, and thus if the process shall stop. : : stack | +----------------+ | +-------->| : | | | | (FRAME_OFFSET) | | | | : | (PC_ADJUST) | | layout:| return_address ----------------+ | | | .... | | +--------------- next_frame | | | | .... | | | | | | | +----------------+ | +-----+ | | : |<- Base fp | | : | | | (FRAME_OFFSET) | (FRAME_LEVEL) | | : | | | : | +---> | [1] | layout:| return_address --------------------> | [0] | | ... | (PC_ADJUST) +-----+ +---------- next_frame | traceback[] | ... | | | +----------------+ o BASE_SKIP, Since we inherently deal with return addresses, there is an implicit shift by at least one for the initial point we are able to observe in the chain. On some targets (e.g. sparc-solaris), the first return address we can easily get without special code is even our caller's return address, so there is a initial shift of two. BASE_SKIP represents this initial shift, which is the minimal "skip_frames" value we support. We could add special code for the skip_frames < BASE_SKIP cases. This is not done currently because there is virtually no situation in which this would be useful. Finally, to account for some ABI specificities, a target may (but does not have to) define: o FORCE_CALL, to force a call to a dummy function at the very beginning of the computation. See the PPC AIX target for an example where this is useful. o FETCH_UP_FRAME, to force an invocation of __builtin_frame_address with a positive argument right after a possibly forced call even if FRAME_LEVEL is 0. See the Sparc Solaris case for an example where this is useful. */ /*------------------------------ PPC AIX -------------------------------*/ #if defined (_AIX) #define USE_GENERIC_UNWINDER struct layout { struct layout *next; void *pad; void *return_address; }; #define FRAME_OFFSET 0 #define PC_ADJUST -4 #define STOP_FRAME(CURRENT, TOP_STACK) ((void *) (CURRENT) < (TOP_STACK)) /* The PPC ABI has an interesting specificity: the return address saved by a function is located in it's caller's frame, and the save operation only takes place if the function performs a call. To have __gnat_backtrace retrieve it's own return address, we then define ... */ #define FORCE_CALL #define FRAME_LEVEL 1 #define BASE_SKIP 1 /*---------------------------- PPC VxWorks------------------------------*/ #elif defined (_ARCH_PPC) && defined (__vxworks) #define USE_GENERIC_UNWINDER struct layout { struct layout *next; void *return_address; }; #define FORCE_CALL #define FRAME_LEVEL 1 /* See the PPC AIX case for an explanation of these values. */ #define FRAME_OFFSET 0 #define PC_ADJUST -4 #define STOP_FRAME(CURRENT, TOP_STACK) ((CURRENT)->next == 0) #define BASE_SKIP 1 /*-------------------------- Sparc Solaris -----------------------------*/ #elif defined (sun) && defined (sparc) #define USE_GENERIC_UNWINDER /* These definitions are inspired from the Appendix D (Software Considerations) of the SPARC V8 architecture manual. */ struct layout { struct layout *next; void *return_address; }; #define FRAME_LEVEL 0 #define FRAME_OFFSET (14 * (sizeof (void*))) #define PC_ADJUST 0 #define STOP_FRAME(CURRENT, TOP_STACK) \ ((CURRENT)->return_address == 0|| (CURRENT)->next == 0 \ || (void *) (CURRENT) < (TOP_STACK)) /* The sparc register windows need to be flushed before we may access them from the stack. This is achieved by way of builtin_frame_address only when the "count" argument is positive, so force at least one such call. */ #define FETCH_UP_FRAME_ADDRESS #define BASE_SKIP 2 /* From the frame pointer of frame N, we are accessing the flushed register window of frame N-1 (positive offset from fp), in which we retrieve the saved return address. We then end up with our caller's return address. */ /*------------------------------- x86 ----------------------------------*/ #elif defined (i386) #ifdef __WIN32 #include <windows.h> #define IS_BAD_PTR(ptr) (IsBadCodePtr((void *)ptr)) #else #define IS_BAD_PTR(ptr) 0 #endif #define USE_GENERIC_UNWINDER struct layout { struct layout *next; void *return_address; }; #define LOWEST_ADDR 0 #define FRAME_LEVEL 0 #define FRAME_OFFSET 0 #define PC_ADJUST -2 #define STOP_FRAME(CURRENT, TOP_STACK) \ (IS_BAD_PTR((long)(CURRENT)->return_address) \ || (unsigned int)(CURRENT)->return_address < LOWEST_ADDR \ || (CURRENT)->return_address == 0|| (CURRENT)->next == 0 \ || (void *) (CURRENT) < (TOP_STACK)) #define BASE_SKIP 1 /* On i386 architecture we check that at the call point we really have a call insn. Possible call instructions are: call addr16 E8 xx xx xx xx call reg FF Dx call off(reg) FF xx xx lcall addr seg 9A xx xx xx xx xx xx This check will not catch all cases but it will increase the backtrace reliability on this architecture. */ #define VALID_STACK_FRAME(ptr) \ (!IS_BAD_PTR(ptr) \ && (((*((ptr) - 3) & 0xff) == 0xe8) \ || ((*((ptr) - 5) & 0xff) == 0x9a) \ || ((*((ptr) - 1) & 0xff) == 0xff) \ || (((*(ptr) & 0xd0ff) == 0xd0ff)))) /*------------------------------- mips-irix -------------------------------*/ #elif defined (__mips) && defined (__sgi) #define USE_GCC_UNWINDER #define PC_ADJUST -8 #endif /*---------------------------------------------------------------------* *-- The post GCC 3.3 infrastructure based implementation --* *---------------------------------------------------------------------*/ #if defined (USE_GCC_UNWINDER) && (__GNUC__ * 10 + __GNUC_MINOR__ > 33) /* Conditioning the inclusion on the GCC version is useful to avoid bootstrap path problems, since the included file refers to post 3.3 functions in libgcc, and the stage1 compiler is unlikely to be linked against a post 3.3 library. It actually disables the support for backtraces in this compiler for targets defining USE_GCC_UNWINDER, which is OK since we don't use the traceback capablity in the compiler anyway. The condition is expressed the way above because we cannot reliably rely on any other macro from the base compiler when compiling stage1. */ #include "tb-gcc.c" /*------------------------------------------------------------------* *-- The generic implementation based on frame layout assumptions --* *------------------------------------------------------------------*/ #elif defined (USE_GENERIC_UNWINDER) #ifndef CURRENT_STACK_FRAME # define CURRENT_STACK_FRAME ({ char __csf; &__csf; }) #endif #ifndef VALID_STACK_FRAME #define VALID_STACK_FRAME(ptr) 1 #endif #ifndef MAX #define MAX(x,y) ((x) > (y) ? (x) : (y)) #endif /* Define a dummy function to call if FORCE_CALL is defined. Don't define it otherwise, as this could lead to "defined but not used" warnings. */ #if defined (FORCE_CALL) static void forced_callee () {} #endif int __gnat_backtrace (void **array, int size, void *exclude_min, void *exclude_max, int skip_frames) { struct layout *current; void *top_frame; void *top_stack; int cnt = 0; /* Honor FORCE_CALL when defined. */ #if defined (FORCE_CALL) forced_callee (); #endif /* Force a call to builtin_frame_address with a positive argument if required. This is necessary e.g. on sparc to have the register windows flushed before we attempt to access them on the stack. */ #if defined (FETCH_UP_FRAME_ADDRESS) && (FRAME_LEVEL == 0) __builtin_frame_address (1); #endif top_frame = __builtin_frame_address (FRAME_LEVEL); top_stack = CURRENT_STACK_FRAME; current = (struct layout *) ((size_t) top_frame + FRAME_OFFSET); /* Skip the number of calls we have been requested to skip, accounting for the BASE_SKIP parameter. FRAME_LEVEL is meaningless for the count adjustment. It impacts where we start retrieving data from, but how many frames "up" we start at is in BASE_SKIP by definition. */ skip_frames = MAX (0, skip_frames - BASE_SKIP); while (cnt < skip_frames) { current = (struct layout *) ((size_t) current->next + FRAME_OFFSET); cnt++; } cnt = 0; while (cnt < size) { if (STOP_FRAME (current, top_stack) || !VALID_STACK_FRAME((char *)(current->return_address + PC_ADJUST))) break; if (current->return_address < exclude_min || current->return_address > exclude_max) array[cnt++] = current->return_address + PC_ADJUST; current = (struct layout *) ((size_t) current->next + FRAME_OFFSET); } return cnt; } #else /* No target specific implementation and neither USE_GCC_UNWINDER not USE_GCC_UNWINDER defined. */ /*------------------------------* *-- The dummy implementation --* *------------------------------*/ int __gnat_backtrace (array, size, exclude_min, exclude_max, skip_frames) void **array ATTRIBUTE_UNUSED; int size ATTRIBUTE_UNUSED; void *exclude_min ATTRIBUTE_UNUSED; void *exclude_max ATTRIBUTE_UNUSED; int skip_frames ATTRIBUTE_UNUSED; { return 0; } #endif #endif